EP0647347B1 - Systeme d'imagerie par irradiation combinant les signaux de sorties de detecteurs. - Google Patents

Systeme d'imagerie par irradiation combinant les signaux de sorties de detecteurs. Download PDF

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Publication number
EP0647347B1
EP0647347B1 EP93916794A EP93916794A EP0647347B1 EP 0647347 B1 EP0647347 B1 EP 0647347B1 EP 93916794 A EP93916794 A EP 93916794A EP 93916794 A EP93916794 A EP 93916794A EP 0647347 B1 EP0647347 B1 EP 0647347B1
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Prior art keywords
detector
digital
output
detectors
signals
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English (en)
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EP0647347A4 (fr
EP0647347A1 (fr
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John L. Couch
Horst Bruening
Guenter Hahn
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Siemens AG
GE Medical Systems Global Technology Co LLC
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Siemens AG
Imatron Inc
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5205—Devices using data or image processing specially adapted for radiation diagnosis involving processing of raw data to produce diagnostic data
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/02—Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computerised tomographs
    • A61B6/032—Transmission computed tomography [CT]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T9/00—Image coding
    • G06T9/007—Transform coding, e.g. discrete cosine transform

Definitions

  • the present invention relates generally to radiation imaging systems, and more particularly to apparatus for reducing the complexity of the analog-to-digital processors and the number of downstream channels required to process x-ray detector output signals in such systems.
  • Computed tomography X-ray systems generate an infinite set of X-ray beam projections through an object to be examined.
  • the resultant detected X-ray data are computer processed to reconstruct a tomographic image-slice of the object.
  • CT systems subject the object under examination to one or more pencil-like X-ray beams from all possible directions.
  • X-ray beams passing through the object are attenuated by various amounts, depending upon the nature of the object traversed (e.g., bone, tissue, metal).
  • One or more X-ray detectors disposed on the far side of the object, receive these beams and provide analog output signals proportional to the strength of the incoming X-rays. Each detector output is then digitized and computer processed to help produce an image of a slice of the object.
  • a CT system would have an infinitely large number of extremely tiny closely-spaced detectors (or fewer detectors repositionable to an infinite number of very closely spaced locations). Because of limitations imposed by economics and hardware, practical CT systems process X-ray beam data from hundreds or thousands of detectors (or detector positions). However, the cost of analog-to-digital ("A/D") conversion of the output of hundreds or thousands of detectors can be prohibitive.
  • the present invention discloses an apparatus and method for reducing the complexity of A/D converters required by CT systems, as well as the number of digitized information channels to be computer processed, without substantial degradation of the image produced.
  • a "first generation" CT scanner configuration is schematically depicted in Figure 1A, and includes a single X-ray source (S), and a single detector (D), both of which move in a translate-rotate fashion (indicated by arrows T, R) relative to the object under examination (O).
  • the translate-rotate movement causes the X-ray beam B to pass through the object O from all directions, with the moving detector D providing an analog output signal at many detector positions responsive to the various beam paths.
  • a signal processing mechanism (SP) digitizes the output of D and ultimately reconstructs an image of a slice of the object O.
  • Figure 1A depicts detector D and source S rotating with an equal radius about the object O, but in practice these radii need not be equal.
  • relative motion between the object and the source and detector is all that is required, and in some applications the detector D and source S are stationary and the object O is rotated.
  • some industrial CT scanners that image large objects an airplane wing, for example
  • Figure 1B depicts a second generation scanner wherein a source S emits an X-ray fan beam B, portions of which pass through the object O and are detected by a single detector D, where both source and detector move in a translate-rotate fashion. Because a fan beam of X-rays is used, the system of Figure 1B can complete a scan more quickly than the system of Figure 1A. For example, if the fan beam B comprises N rays, object O may be scanned N times faster than the first generation system of Figure 1A wherein there is but one ray. For ease of illustration, Figure 1B depicts a small number of rays, but fan beam B actually includes a continuum of rays.
  • detector D and source S need not be equidistant from the object O, and that relative motion between the object and the source and detector is all that is required.
  • a signal processing mechanism digitizes the detector output and provides an image of a slice of the object O.
  • Figure 1C depicts a third generation CT scanner system having a point X-ray source S and multiple detectors D i arranged in an arc, where point source S and the array of detectors D i rotate relative to the object O, but there is no translational movement.
  • the single detector of Figure 1A could be relatively rotated in an arc to various detector positions corresponding to D i , it could serve as the plurality of detectors shown in Figure 1C. Again, the radii of relative motion are drawn equal for ease of illustration only.
  • a signal processing mechanism digitizes the detector outputs and provides an image of a slice of the object O.
  • SP signal processing mechanism
  • Figure 1D depicts a fourth generation CT scanner system as including a source S that emits an X-ray fan beam B and an array of detectors D i , wherein the source S rotates relative to the object O, the detector array is stationary, and no translational movement of source or detectors occurs.
  • the detector array and X-ray source are drawn as being equidistant from the object O merely for ease of illustration.
  • a signal processing mechanism (SP) digitizes the detector outputs and provides an image of a slice of the object O.
  • FIG. 1E depicts in greater detail a fourth generation scanning electron beam CT system such as described generally in U.S. Patent US-A-4 352 021 to Boyd, et al., (September 28, 1982).
  • CT system 10 of Figure 1E there is a housing chamber 12 wherein an electron beam 14 is generated and caused by a beam optics assembly 16 to scan an arc-like typically tungsten target 18 located within chamber 12's front lower portion 20.
  • the target Upon being struck by the electron beam, the target emits a moving fan-like beam of X-rays 22. At least some of these X-ray beams pass through a region of object 24 and then register upon a region of a detector array 26 located generally diametrically opposite that portion of target 18 struck by the electron beam 14.
  • the detector array includes a relatively large number of detectors D (perhaps 2,000-5,000) that sequentially receive at least a portion of the moving beam of X-rays.
  • Each detector's output is an analog signal typically representing a few nA of current, which signal is passed through a current-to-voltage converter (not shown) to yield an analog signal of perhaps several hundred mV.
  • a current-to-voltage converter not shown
  • each detector output is lowpass filtered (filters not shown) to remove frequency components higher than about 25 KHz.
  • the analog detector outputs are then digitalized using analog to digital (“A/D”) converters.
  • blocks of analog detector outputs are typically multiplexed.
  • the multiplexed outputs are then digitised using A/D converters, with fewer A/D converters required because of the multiplexing.
  • DAS Digital Acquisition System
  • the digitalized signal channels from the A/D converters are then coupled to a computer system 32 where they are extensively processed to produce an image of a slice of the X-rayed subject on a high resolution video monitor 34.
  • computer system 32 also controls reading of the various detectors, electron beam scanning, and repositioning of the X-rayed subject 24.
  • the signal processing mechanism (SP) depicted therein may be thought of as including elements 30, 32 and 34 as depicted in Figure 1E.
  • Figure 1E helps demonstrate that in reconstructing a tomographic image from X-ray detector data, it is unimportant how the X-ray beams were caused to traverse the object O.
  • Figure 1E depicts a scanning electron beam system
  • Such a scanner system is in fact depicted in U.S. Patent US-A-4 630 202 to Mori (December 16, 1986), which describes a third generation system.
  • the moving source of X-ray beams or fan beams could be produced by rotating an X-ray source of such beams, or by scanning a stationary X-ray emitting target with a moving electron beam (as is done in Figure 1E).
  • Figure 2 is a detailed depiction of the contents of the DAS 30 in Figure 1E, and depicts a prior art technique for reducing the number of A/D converters and resultant digitalized information channels that require computer processing. Figure 2 also depicts several relationships required to reconstruct an image from CT data.
  • the isocenter 21 for a scanner system 10.
  • the isocenter is the center of a fictitious image reconstruction circle 23, within whose circumference must lie the object O to be scanned and suitably reconstructed.
  • isocenter 21 is also the center of the array 25 of the detectors D i , and the center of the X-ray beam source or scan path 27 (which coincides with target 18 in the embodiment of Figure 1E).
  • the region within the circle 23 must be exposed to X-ray beams from all possible directions.
  • FIG. 2 The depiction of Figure 2, wherein the vortex of the beam fans shown is a source point is termed a "source fan".
  • a source fan depiction it is understood that at any given time, an X-ray fan beam simultaneously strikes many detectors.
  • a fan beam such as B t is actually a continuum comprising a large number of X-ray beams.
  • FIG. 1A-1E The relationship between the isocenter, the image reconstruction circle, the location of the detector(s) and X-ray source or X-ray beam source exists for any of the systems shown in Figures 1A-1E. While Figure 2 depicts the X-ray source or X-ray beam source as being radially more distant from the isocenter than the detectors, the converse could be true, or in a suitable arrangement equal distances could be employed. Any of the CT systems shown in Figures 1A-1E can suitably reconstruct any image O lying within the reconstruction circle 23. Note in Figure 2 that the lower ends of the detector array 25 extend at least to (and preferably slightly beneath) the lower edge of the reconstruction circle 23, while the upper ends of the scan path 27 extend to (and preferably slightly above) the upper edge of the reconstruction circle 23. This configuration ensures that any point within circle 23 is scanned from every possible direction (including horizontally), and that all X-ray beams fall at least partially on a portion of the detector array 26.
  • Detector array 26 in Figure 1E preferably may include as many as 4,800 detectors (or detector positions) spaced apart a distance d about 1 mm or 0.1° (see Figure 3). However for ease of illustration only nine such detectors (D 1 , D 2 , ... D 9 ) are depicted in Figure 2, disposed along arc 25. Because the X-ray fan beam 22 is depicted by arrow 28 as moving clockwise, it is understood that detector D 1 is scanned first by the beam 22, then detector D 2 , D 3 and so forth. For example, at an arbitrary time t, a fan beam B t is emitted at a position S t along the tungsten target 18 (see Figure 2).
  • the electron beam 14 (see Figure 2) scans position S t+1 along the target 18 and a fan beam B t+1 results.
  • the result is a scanning fan beam B that sweeps clockwise along arc 27 in Figure 2.
  • the electron beam 18 preferably scans about 210° along the target 18 in perhaps 50 mS to 100 mS.
  • Figure 2 does not depict the current to voltage conversion ("I/V") for each detector output, or any filtering to limit higher frequency detector output components.
  • I/V current to voltage conversion
  • a given detector is activated and its output sampled every 10 ⁇ s to every 50 ⁇ s or so.
  • This selective detector activation preferably controlled by computer system 32, promotes efficient signal processing because time is not wasted sampling detectors having no meaningful output to contribute to the reconstructed image.
  • detectors D 1 , D 2 , and D 3 may be multiplexed together using multiplexer 40, whose single analog output is digitized with an A/D converter 42.
  • outputs from detectors D 4 , D 5 , D 6 and D 7 , D 8 , D 9 may be multiplexed using multiplexers 44 and 48, respectively, whose single outputs are then digitized by A/D converters 46 and 50, respectively. It is of course not necessary that the multiplexed detectors be adjacent to each other, only that they not be simultaneously converted.
  • the number of required A/D converters is reduced to one-third.
  • the use of multiplexers can reduce the number of required A/D converters from about 4,800 to about 1,700.
  • Unfortunately providing a CT system with 1,700 A/D converters is still rather expensive, and still represents approximately 1,700 channels of digitized signal data to be computer processed downstream.
  • an apparatus for combining detector output signals in a radiation imaging system that not only reduces the number of information channels to be processed (using multiplexers) but also reduces the complexity of the A/D conversion circuitry and the associated delay and combining circuitry. Additionally, it is important that such apparatus and method should not substantially degrade the resultant video image, should be relatively inexpensive to implement, and preferably should operate in real time in a conventional CT system.
  • the present invention discloses such an apparatus.
  • an embodiment of the present invention can provide a system for reducing the complexity of A/D converters and downstream processing in a CT system and by combining two or more detectors into a pseudo detector, whose single output is then processed for forming a CT image.
  • the pseudo detector can be created from a single detector that is sequentially repositioned.
  • the sigma delta A/D converter preferably provides a reduced width bit stream representative of the analog signals.
  • a sigma delta converter receives an amplified and level shifted analog signal from each x-ray detector and provides on a serial output (that is, a one bit wide bit stream) multi-bit digital words representative of amplitude changes of the analog signals.
  • a simple digital delay device such as a shift register, can then be used for simply and reliably establishing a time delay between the single bit wide bit streams in the signal processing channels for adjacent detectors.
  • a relatively simple digital combining means can be used for adding together the single bit wide bit streams in the signal processing channels for adjacent detectors.
  • a relatively simple digital combining means can be used for adding together the single bit wide bit stream for adjacent detector channels for forming the multi-bit wide bit streams which are then processed in the conventional manner for developing the CT image.
  • a current sensitive modulator portion of the delta sigma A/D converter is separated from its filtering section, so that amplification and level shifting circuitry is not required at the input to the delta sigma modulator. This greatly reduces the circuit complexity of the signal processing circuitry.
  • Delay means is then coupled to the output of the delta sigma modulator for providing a time delay between adjacent detector signal processing channels.
  • the reduced-width bit streams can be combined, registered and offset corrected as in the previously described embodiment, or alternatively, multi-bit width digital words can be formed for each detector signal processing channel by digital low pass filtering and decimation.
  • the digital low pass filtering and decimation could occur after the adjacent detector channels have been combined, or the digital filtering can be apportioned so as to be partially before and after the adjacent detector channel combining.
  • Embodiments of the present invention can provide a reconstructed CT video image substantially without degradation. While more than two detectors can be combined in a pseudo detector, the quality of the reconstructed image is preserved when the number of detectors comprising a pseudo detector is small. Having a small number of combined detectors promotes close proximity of the detectors or detector positions comprising the pseudo detector, and ensures that data obtained from each detector represent an X-ray beam passing through substantially the same region of the CT system reconstruction circle.
  • the present invention reduces the complexity of the A/D converters in a CT system by combining two or more detector outputs to create a pseudo detector, whose single output is then processed.
  • a pseudo detector according to the present invention can combine multiple outputs from a single detector that is sequentially repositioned. Contrary to conventional wisdom, applicant has discovered that an image reconstructed from the output of pseudo detectors will not be substantially degraded.
  • a pseudo detector is implemented by creating narrow-width bit streams representative of the analog output read from detectors that see X-ray beams having substantially the same Radon radius, which beams preferably see substantially the same region of the object under examination, establishing a time delay between the detector outputs, and then combining the detector outputs to form a relatively wide bit width bit stream.
  • a pseudo detector For cylindrically symmetrical objects under examination (e.g., a perfect tree log) applicant's pseudo detectors provide an exact method, even if the detectors (or detector positions) are widely spaced. For other objects, the method is inexact but acceptable, especially where the detectors forming the pseudo detector are in relatively close proximity to one another so that substantially the same X-ray beam is received by each detector.
  • the delay time ⁇ is a function of the geometry of detector arc 25, the location of the detectors (or detector positions) comprising detector array 26 along that arc, the geometry of the X-ray source arc 27, and the rapidity with which the X-ray source is moved along arc 27.
  • the desired delay time ⁇ (or delay times if ⁇ is not a constant) is known, and preferably is maintained within about ⁇ 5% to minimize image degradation according to the present invention.
  • Figure 3 is a basic block diagram for a digital acquisition system (DAS) for use as a replacement for box 30 in a system such as shown in Figure 2.
  • DAS digital acquisition system
  • adjacent detectors D i and D i+1 are digitized so as to produce relatively narrow bit width streams representative of the detector analog signals.
  • the digitization is accomplished using delta sigma A/D converters 310 and 312, which each provide a digital output bit stream having a bit width which is substantially less than the bit width developed for each detector signal in accordance with the prior art.
  • a digital time delay means 314 establishes the required time delay ( ⁇ ) between the adjacent signals. Due to the narrow width bit stream for each channel, the time delay means 314 can be realized using a relatively simple, reliable and low cost digital circuit, such as an A-bit wide shift register, where A equals the width of the narrow bit stream provided by digitizer 310.
  • N total number of detectors forming the pseudo detector
  • i the number of detector within the group
  • ⁇ the time taken for the beam to traverse from one detector to the next.
  • the system shown in Figure 3 employs only two detectors in the pseudo detector group, although any number of detectors can be grouped together.
  • FIR filters and appropriate decimation circuitry can be utilized, such as illustrated by optional digital filtering circuits 316 and 318. Since noise filtering and signal shaping of the x-ray detector signal is required in any event, such filtering can be conveniently combined and incorporated into the digital filtering necessary for completing the delta sigma A/D converter, thereby resulting in a negligible increase in the digital circuitry required to accomplish the present invention, as compared with the prior art.
  • the filtering is done in the digital domain, symmetric impulse response signal shaping is possible, as compared with the less desirable asymmetrical signal shaping performed by the analog filters of the prior art embodiments.
  • the output of the signal combiner and filter circuit 320 is then a full bit width digital word representation of the combined adjacent detector signals (the pseudo detector) whose single output signal on line 322 may thereafter be processed as in the prior art for developing the CT images.
  • the circuitry required for combining the reduced bit width bit streams comprises a relatively simple adder circuit and the digital filtering aspects of combiner 320 comprise recursive filters such as those commonly used in delta sigma A/D converters, as well known to those skilled in the art.
  • Figure 4 illustrates an embodiment using currently available components.
  • A/D converters 418 and 420 may comprise Model No. CS5338 A/D Converters available from Crystal Semiconductor Corportion.
  • time delay ( ⁇ ) is accomplished by using the digital power-down command of the A/D converter chip (pin 10 of ICCS5338).
  • the same clock can be used to drive all of the A/D converters in the DAS. More specifically, after A/D converters 418 and 420 are put into the power-down mode, converter 418 is put into the active state, which starts an internal calibration cycle having exactly m clock cycles. The power-up (or release) of converter 420 is delayed by the desired delay time ( ⁇ ) to be established between the adjacent detectors, which then starts exactly the same calibration cycle as in converter 418. Thus, the first conversion from converter 418 will be exactly the desired time delay apart from the first one of converter 420.
  • the combiner reads the first conversion output from converter 418, which was held in a temporary storage device 422, such as a FIFO.
  • a temporary storage device 422 such as a FIFO.
  • Combiner 424 also provides offset correction, as necessary, which offsets one inherent in A/D conversion.
  • FIFO 422 acts as a buffer to hold the output of converter 418 until the delayed output from converter 420 is ready to be added to it via combining circuitry 424.
  • digital filtering and decimation which is conventional for A/D converters of the delta-sigma type, is included within converters 418 and 420 and their outputs each comprise a serial bit stream of, for example, 16-bit words.
  • the digital filtering used in converters 418 and 420 advantageously includes that filtering conventionally necessary in CT detector channel processing.
  • Figure 5 illustrates a more cost-efficient circuit topology for the present invention.
  • the modulator portion of the A/D converter is separated from the filtering portion, so that a simple one-bit wide shift register can be used for establishing the time delay, tau.
  • detector output signals D i and D i+1 are connected so as to directly provide a current input to the modulator portion of a delta sigma modulator, such as the modulator described in the forenoted "Application Note AN10REV1" which is used in the delta-sigma A/D converters available from Crystal Semiconductor Corporation.
  • the transimpedance amplifiers and analog gain and level shifting circuitry required in the Figure 4 embodiment are not necessary in this preferred embodiment.
  • impulse response filtering such as a digital low-pass filter
  • decimation is provided for each bit stream by digital filters 514 and 516.
  • the filter outputs are then applied to a digital combining circuit 518 for providing an M-bit wide output signal for further processing and developing of the CT image. Due to cost constraints and a users trade-off between resolution (bit width) and digitizing rate, the amount of digital filtering and decimation which occurs before and/or after signal combiner 518 can vary. Thus, more specific guidelines concerning the bit width (n) of the signals provided into combiner 518 cannot be given.
  • a prior art CT system will typically employ a certain number of detectors and A/D converters.
  • the present invention enables a CT system to be constructed with considerably more detectors but with less complex A/D converters and downstream processing components, the result being a superior quality reconstructed image.
  • the present invention enables a CT system to be built for fewer dollars by using the same number of detectors as an existing system, but with less complex A/D converters and fewer downstream processing components, the result being a more competitively priced system.

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Claims (9)

  1. Un système d'imagerie par irradiation comprenant :
    une source d'irradiation (28) pour produire au moins un faisceau d'irradiation qui traverse au moins une région sous investigation (23) ;
    un ensemble de détecteurs espacés (Di) dont chacun est actionnable pour produire un signal de sortie analogique en réponse à un faisceau d'irradiation ; et
    un moyen de numérisation (418 ; 420 ; 510) permettant de numériser des signaux de sortie respectifs produits par les détecteurs afin de donner des signaux numériques respectifs de largeur de bit relativement étroite pour produire des signaux numérisés de sortie des détecteurs,
       caractérisé par des moyens de combinaison actionnables pour combiner des signaux numérisés d'un groupe de pseudo détecteurs de N détecteurs qui ont sensiblement le même rayon Radon, où N est au moins égal à deux, les moyens de combinaison comprenant :
    des moyens numériques à retard (314 ; 422 ; 513) actionnables pour retarder le signal numérisé de sortie de détection de chaque détecteur du groupe de pseudo détecteurs d'un temps respectif ti = (N-i) τ, où i est égal au nombre des détecteurs concernés dans le groupe de pseudo détecteurs, et τ est le temps qui s'écoule entre l'instant où le faisceau tombe sur un détecteur du groupe et l'instant où il tombe sur le détecteur suivant; et
    une unité de combinaison (320 ; 424 ; 518) pour recevoir les signaux numérisés retardés de sortie des détecteurs, et pour produire un signal numérique de sortie combiné présentant une grande largeur de bit par rapport à ladite largeur de bit étroite, le signal de sortie combiné étant utilisé pour reconstruire une image de la région sous investigation.
  2. Un système tel que revendiqué à la revendication 1, dans lequel le moyen de numérisation comprend un modulateur sigma delta (310, 312, 418, 420) pour chacun des N détecteurs du groupe de pseudo détecteurs.
  3. Un système tel que revendiqué à la revendication 2, dans lequel l'unité de combinaison comprend un additionneur numérique à largeur de bit étroite (320, 424, 518) et un premier filtre numérique utilisable pour reconstruire une image de ladite région intéressante.
  4. Un système tel que revendiqué à la revendication 3, dans lequel un second filtre numérique (316, 318, 514, 516) est couplé à la sortie de chaque modulateur sigma delta (310, 312, 510, 512) pour produire un ensemble de signaux numériques de largeur de bit étroite en série, où au moins deux signaux prévus en série correspondent au signal de sortie du même détecteur, les moyens numériques à retard (314, 518) étant couplés entre la sortie du modulateur sigma delta et le second moyen à filtre.
  5. Un système tel que revendiqué à la revendication 4, dans lequel le second filtre numérique (316, 318, 514, 516) comprend un filtre FIR numérique et un décimateur.
  6. Un système tel que revendiqué dans une quelconque des revendications 2 à 5, dans lequel un filtre numérique de sortie (316, 318, 514, 516) est couplé à la sortie du modulateur sigma delta (310, 312, 510, 512) pour créer des signaux numériques d'une manière parallèle, et dans lequel les moyens numériques à retard (314, 513) sont couplés entre la sortie des moyens à modulateur sigma delta et l'entrée du filtre numérique de sortie.
  7. Un système tel que revendiqué dans une quelconque des revendications précédentes, dans lequel les signaux numériques de largeur de bande étroite comprennent un courant de bit numérique de la largeur d'un bit.
  8. Un système tel que revendiqué à la revendication 7, dans lequel les moyens numériques à retard comprennent un dispositif mémoire à registre de décalage numérique du type premier entré - premier sorti (422).
  9. Un système d'imagerie par irradiation tel que revendiqué dans une quelconque des revendications précédentes, dans lequel le faisceau d'irradiation est un faisceau à rayons X, le système étant un système à rayons X de tomographie informatisée.
EP93916794A 1992-06-26 1993-06-28 Systeme d'imagerie par irradiation combinant les signaux de sorties de detecteurs. Expired - Lifetime EP0647347B1 (fr)

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US90500992A 1992-06-26 1992-06-26
US905009 1992-06-26
PCT/US1993/006116 WO1994000850A1 (fr) 1992-06-26 1993-06-28 Procede et appareil d'association de sorties de detecteurs faisant partie d'un systeme d'analyse tomographique par ordinateur

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EP0647347A1 EP0647347A1 (fr) 1995-04-12
EP0647347A4 EP0647347A4 (fr) 1995-05-24
EP0647347B1 true EP0647347B1 (fr) 1998-09-02

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WO (1) WO1994000850A1 (fr)

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US9192341B2 (en) 2012-02-13 2015-11-24 Siemens Aktiengesellschaft Computed tomography device and method for operating a computed tomography device

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DE69320814D1 (de) 1998-10-08
DE69320814T2 (de) 1999-01-14
JPH07508202A (ja) 1995-09-14
WO1994000850A1 (fr) 1994-01-06
EP0647347A4 (fr) 1995-05-24
EP0647347A1 (fr) 1995-04-12
US5448609A (en) 1995-09-05

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